Tubes are in common use in various heat exchanger apparatuses such for example as boilers and condensers. The tubes employed in a boiler are commonly exposed to hostile elements such as fly ash. These hostile elements can have the effect of abrading and corroding the tubes with the result that the tubes experience early failure resulting in major maintenance and significant boiler downtime costs.
Many devices have been devised to protect the tubes from the hostile elements. In one such protective device, the shield includes an axially elongated protector member of arcuate cross section sized to fit over the tube to protect the portion of the tube embraced between the axial free edges of the member and straps are welded to the axial free edges of the member after the member has been fitted over the tube to maintain the protector in its protective position around the tube. Whereas this protective device has seen considerable usage, it suffers from the disadvantage that it requires shop labor to weld the straps between the axial free edges of the protector and, further, the welding in the vicinity of the tube may have the effect of altering the chemistry of the tube with resultant metal fatigue.
In another such protective device, also involving an axially elongated protector member of arcuate cross section, the axial free edges of the protector member are rolled radially outwardly and the inner surfaces of the rolled edges are spaced apart a distance less than the diameter of the tube to be protected so that the protector member may be snapped in place over the tube with the rolled axial free edges of the protector member engaging the tube to inhibit separation of the protector member from the tube. Whereas this device has also seen considerable usage, it suffers from the disadvantage that the radially outwardly rolled free edges of the protector member extend into the flow path between adjacent tubes so as to interfere with gas flow between adjacent tubes and, further, the rolled free edges, in order to have the required spring action to retain the protector member on the tube, must be relatively thick and this thickness of necessity must be carried through the entire protector member with the result that the protector member is heavier and more expensive than it need otherwise be to perform its protective function.